Low Pressure Discharge Characteristics in a Large Sized Hollow Cathode

Abstract

This work presents the experimental and theoretical research of low pressure discharge characteristics in a large sized hollow cathode using treated work pieces. The dependence of discharge voltage on gas pressure and system geometry has been obtained. It is demonstrated that the high plasma homogeneity with concentration up to 1012 cm2 and plasma temperature within the order of 1 eV is obtained. It is shown that the external discharge current enables the independent control of discharge current and its voltage.

Mathematical Modeling of Discharge Plasma Generation and Diffusion Saturation of Metals and Alloys

“…1 [8,9]. Anode 1 in the form of two tubes of total area S a is located at the side wall of the cathode.…”

“…To determine the spatial distribution of the electron temperature and plasma density and to study the effect of the geometry, size, and material of targets placed in the cathode cavity, we used a hydrodynamic model, which describes the density of charged particles and their average energy as a function of time and space [9]. This model describes the electron charge densities (n e ) and their average energies (n  ) as function of the time and space:…”

“…Fig. 2 shows calculated (formula (2)) and experimental dependences [8,9] of the discharge operating voltage on the gas pressure (argon, nitrogen) in the selfsustained mode at different effective lengths of the hollow cathode L = 4V/S a ; the discharge current is 30 A; the experimental values correspond to S a = 500 cm 2 . Decreasing the operating pressure of the main discharge causes a substantial increase in discharge operating voltage at a pressure below 0.65 Pa. At these pressures, a large fraction of ionizing electrons whose energy is only partly expended in ionization reaches the anode.…”

“…The vacuum plasma technology used for surface modification of materials and large-size objects is based on the generation of low-temperature glow discharge plasmas [4][5][6][7][8][9] for which it is required to provide an ion current density of ~1 mA/cm 2 to a treated surface and a discharge operating voltage of hundred volts [8][9][10][11].…”